Intertransposition of sound and electrical energy



"N. E. LINDENELAD v INTERTRANSPOSITION OF SOUND AND ELECTRICAL ENERGY Filed Aug. 17, 1927 RdB/0 FREQUENCY INVENTOR BY; A

MLS ELUNDENBLRD A CRNEY Patent Sept., l, 192

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NILSE. LHFDENBLAD, OF SHOE/EMM, NEW YORK, ASSIGNO-R TO RADIO CORPORATION OF AMERICA, A CORPORATION OF DELAWARE.

INTEBTRANSPOSITION OF SOUND AND ELECTRICAL ENERGY.

Application led August 17, 1927. Serial No. 213,567.

This invention relates to the intertransposition of sound and electrical energy, and more particularly to an inertialess speaker for translating electrical energy to sound energy.

Ordinarily electro-acoustic devices possess mass and elasticity, and therefore experience mechanical tuning or natural resonance phenomena which are the cause ofdistortion in the sound or electrical Wave produced. It is clear that an ideal solution of the problem of distortionless reproduction may be obtained by the intei'transposition of sound and electrical energy without the intermediate use of a vibratory device possessing either in- (ertia yor elasticity, and accordingly, it 1s an object of my invention to obtain such intertransposition. I

To do this I produce a' corona' discharge in the air medium which is to carry the sound, and take advantage of the corresponding and related fluctuations of the pressure of -the air, the heating effect of the corona discharge taking place therein, and the electrical energy producing the corona discharge. In the case nf a speaker the corona discharge device is Ienergized by the use of unmodulated energy from some local source of direct or super audible alternating potential, and the corona is modulated y su erimposing on the applied potential energy o audio frequency or modulated ener of high frequency. The local energy, if a ternating, must not only be super audible but must be of such frequency that it will not beat with the modulated'carrier at an audible frequency, that is, their fre uencies should be equal, or should` differ y a super audible frequency. D

The invention 1s more fullyl described in the following specification which is accompanied by a drawing in which Fi re 1 indicates a corona speaker ener-y gizeru by direct current and modulated by audio frequency energy;

Figure 2 shows a corona speaker equipped with a reflector, energized with direct current, and modulated by modulated high frequency energy;

Figure 3 is another view of the speaker shown in Figure 2;

Figure 4 represents the direct eneroization of a corona speaker by modulated h1gh'frequency energy;

Figure 5 shows the use of local high freuency energy to produce the corona disc arge; and

.Figure 6 indicates. the use of a corona device as a microphone.

Referring to Figure 1 there is shown a me'- tallic ball 2 which is studded with a large number of needle points, and which is brought to a high potential by a battery 4 through a power limiting resistance 6. The function of this resistance is to prevent injury in case someone touches the discharge sphere. The conora draws but slight current, and thenormal potential drop across the resistance is small, but upon accidental grounding there is an increase of current which causes a marked decrease inthe potential applied to the sphere. y The corona effect is aided by the proximate juxtaposition of a grounded plate 8, in which the lines of force terminate. Signal energy received on an antenna 10 is rectified by a detector tube 12, the audio frequency output of which is fed to an amplifier 14, from which the audio frequency energy is superimposed on the direct energy from -the battery 4 throughlthe medium of a transformer'l, thus serving to modulate thek corona discharge/ One advantage of the Speaker described is that it is directionless, but if a directional speaker is desired the grounded shield may be made in the form of a parabolic reector, as i's` indicated in Figure 2. Referring to this -fig- 85 ure the corona discharge sphere 2 is located at the focus of a parabolic reflector 18, which is metallic and grounded to terminate tliecorona lines of force, and which preferably is surrounded by a heavy backing of-rubber or other damping mediumV 20, in order to make the reectol Substantially aperi0djc ThiS/s/...- Y l in contrast to the use of a horn, forreveii/the mass of the air columnin-a/horn isto be avoided. n Y. ,I 4 9o In Ythis/"cas, as in the modification shown in Figure 1, the energization is by means of a direct current source 4, but the modulation is obtained directly at radio frequency, signals being picked up on antenna `10 and amplified 100 at radio frequencyin an. amplifier 22. The direct current source may merely bring the potential'up to the critical corona discharge point, if desired, but this is not essentialfor rectification, because the corona phenomenon is one of heating, and depends on the current A squared, and therefore the device is inherently rectifying. v

In Figure 4 the modulatedhigh frequency energy picked up by the antenna 10 and am- 1107 plified in amplifier 22 is fed to ka corona speaker 2 and serves not merely for modulation of the corona, but actually produces it.

In the modification shown in Figure 5 there is a local source of high frequency energy 24 which serves to energize the corona sphere 2, and modulation is obtained, as before, by means of audio frequency or a modulated radio frequenc In the latter case the radio fr uencies s ould either be arranged to homo yne, that is, their fre uencies should be exactly equal, or else shoul differ by a superaudible frequency so -that an audible beat will not be produced, which would otherwise spoil n the reproduction. In case single side band energy is received the loscillator 24 may be used to supply the carrier energy.

In Figure 6 there is indicatedpa corona sphere 2, s'ituat-.edY atthe focus of a parabolic refiector'18fand energized by a direct current source 4. In this case the corona dischar e device is used as a microphone, and soun directed towards the reiector will vary the air pressure in which corona is taking place, andy therefore vary the energy consumednin producing the corona. This enerluctuation ma be coupled through a transformer 16 an led to suitable amplifiers before being used for wire transmission or for modulating high frequency energy for radio transmission.

The discharge needles should preferably be exceedingly sharply pointed in order to keep the necessary otentials aslotv7 asl pos'- sible. The reflecting shield should be grounded, and a protecting cage may be provided, to minimize danger from the high potential. In order to make the reproduction distortionless a straight rtion of the corona curve must be selecte' for the operating range, andl this is quite feasible because of the character of a corona curve.

I claim:

--\al. "I`liel method of intertrahsposing sound and electricalenergy which includes producing a corona disc arge in the air medium Which is to carry the sound, and utilizing the relation between airpressure, the heating eectof the lcorona discharge, and the electrical energy producing it, to obtain intertranspos'ition of sound and electrical energy.

2. he lmethod of translating electrical energy to sound which includes the steps of producin a corona discharge in the air medium which is to carry the sound, and modulating the corona discharge by means of the electrical energy.

3. The method of translating modulated electrical energy to sound which includes using unmodulated electrical energy to produce' a corona discharge in the air medium which is to carry the sound, and modulating the corona discharge by means 'of the modulated electrical energy.

4. An inertialess device for the intertransposition of sound and electical energy comprising a corona discharge point and a .grounded shield cooperating therewith.

5. An inertialess device for the intertransposition of sound and electrical energy coinprising a plurality of corona discharge points and a substantially aperiodic grounded metalla lic reflecting shield cooperating therewith.

6. An ineratialess system for the intertiansposition of sound and electrical energy comprising a corona discharge device, and

electrical circuit for energizing said device,

and means coupled to said circuit in series high frequency electrical energy for energiz-Mv ing said device, and a source of sound variedelectrical energy coupled to said circuit to modulate the intensityof the corona.

9.` In combination, an inertialess speaker comprising a corona discharge device located in the air lmedium which is to carry the sound, a source 0f electrical energy for energizing said device at a constant value, a source of modulated electrical energy arranged t0 modulate the resultant corona, and means for coupling said device and sources electrically in series.

10. In combination, an iutertialess speaker n comprisin a corona discharge device, and means inc uding a radio receiver to energize said device. N

11. An apparatus for translating electrical energy into sound which comprises a corona dischar e device, a source of' alternating current or energizing said device, and

means for supplylng amodulated high frequency current to said device to modulate the corona discharge.

12. A speaker system accordin to claim 7 in which said corona discharge evice comprises a metallic member provided. with a plurality of needlel like points and a grounded plate. I

` NILS E'. LINDENBLA D. y

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CERTIFICATE 0F CORRECTION.

Patent No. 1,685,075. Granted September 18. 192,8, to

NLS E. LINDENBLAD.

It is hereby certified that error appearsin the printed specification oi the above numbered patent requiring correction as follows: Page 2. strike out claim 10. comprising lines 102 to 105; same page, lines 106 and 113, for claim numbers 1l and 12, read 10 and l1; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 11th day of December, A. D. 1928.`

M. J. Moore, (Seal) Acting Commissioner of Patents. 

